RELATIONSHIP BETWEEN SERUM ALPHA-1-ANTICHYMOTRYPSIN AND ALZHEIMERS-DISEASE

We obtained serum samples and measured alpha 1-antichymotrypsin (ACT) levels in 36 pairs of consecutive probable Alzheimer's disease (AD) pa tients and age- and sex-matched, cognitively intact control subjects. Serum ACT was measured by radial immunodiffusion. Unique to this study , we found that ACT levels rose significantly with age within controls (but not within AD cases), thus ACT may be related to the aging proce ss. Consistent with other reports, we found that AD cases had greater serum ACT in 27 of 36 pairs [mean difference = 135.5 (SE = 50.8) mg/l (p<0.05)]. Severity and duration of AD were not significantly associat ed with the observed difference. The ACT increase observed in AD is no t sufficient to recommend ACT's use as a diagnostic marker for AD. Bec ause adult Down's syndrome (DS) persons are known to have pathologic f eatures of AD, we also measured serum ACT levels in 11 adult, noninsti tutionalized, DS persons paired with 11 age- and sex-matched, voluntee r control subjects; we found no statistically significant difference. The unexpected age-associated increase in ACT among normal controls co uld be an indicator of early amyloid prague formation. Future studies comparing ACT levels in both serum and cerebrospinal fluid should help to clarify the origin of ACT found in amyloid plaques and its value a s a diagnostic marker for AD.